Embodiments of the invention relate generally to thermal imaging for deep flaw detection in anisotropic media, and more particularly to two slope reference for synthetic thermal time of flight imaging.
Adjustment of temperature-time (T-t) reference curves, used in thermal imaging, for adaptation to deep flaw detection in anisotropic media is desirable. In such media, the ingoing thermal pulse follows 1-D heat flow while the pulse returning from the flaw to the surface follows 2-D flow since the flaw is typically closer to a point source. Log-log forms of the T-t curves have been used in practice since for 1-D flow they are straight lines of slope −½. Adjustment of the trailing end of the slope can improve the sensitivity to deep flaw imaging. Therefore, joining two lines of variable slope at an adjustable point in time so that its slope is continuous at the junction is desirable.